Prototyping of Complex Bracket for Starting Block - Help with Supplier Selection

Hey Fellow Engineers,

I am working on a part for a starting block for competitive swimming and it is extremely complex. I have had it quoted for stainless steel in CNC, however I just cannot afford to pay over $2,000 for a small prototype. I have heard about this technology from a friend of mine, its called DMLS or Metal Sintering. Has any of you ever used this technology, is it strong like real stainless? Is anyone aware of the costs involved, is it less than CNC? If you have used someone in the past, who was it and were you happy with the outcome? I really appreciate the help.

Shmitty!
Lane 3 Aquatics

 

Schmitty,
I don't have much experience with 3D prototyping, though I have been researching it lately. As a former swimmer, I would guess your parts are pretty large. From my limited knowledge, 3D printing your part in plastic would be rather expensive, so I would guess that metal sintering would be more so. Most starting blocks I remember were tubular stainless construciton with fiberglass tops. I'm not sure if you are going to match the strength of stainless with any material... for a reasonably competitive price. For a prototype, have you considered aluminum? Just some thoughts. Curious to hear your outcomes. Thanks, db

 

Shmitty,
First, is the prototype for just looks to show and evaluate the design or is it to be fully functional for testing? Most times RP is used to validate a design and for a final "that's what I want" evaluation before spending the time and money making a test component. If you are sure that you will not be making changes, then the process of how you would go about mass producing them should be considered. If there are areas of concern in the design, you may be able to make one that is designed with interchangable parts so you can tweek it before committing to the final product. Kind of hard to give you an answer without seeing the part. I have experience in RP as well as machine shop practices and designing around such practices.

David

 

I'll bet that a competent welding shop could make you a prototype for less money than you are being quoted.

 

Shmitty,
If you wish, you could send me a non-disclosure and then what you have as to the design and could provide some better ideas. A weld shop could do it but again it's more a matter viewing in hand vs. practical for testing. There would be no charge and it would be confidential.

David

 

Shmitty,
Based on the image of your starting block on your website would say that 3D printing (additive fabrication) of a full sized prototype would be quite expensive (especially if you're thinking of metal sintering) - likely well north of $2k. So if you're looking for a full size model, I'd go with the more traditional fabrication.

However, if you're looking for a scale model to 3D printing could be your best bet. And depending on material/technology and supplier it might even be cheaper than traditional fabrication. Faster also. But build envelopes are in the 12" x 8" x 8" range so think of appropriate scaling or printing your model in parts. Also, due to cost, metal prototyping is probably not an option so let me give a brief (non-exhaustive) overview of plastic and other material 3D printing.

The original 3D printing, developed in the 1980 was SLS. The parts are extremely high resolution but very fragile and expensive. Plus it's slow.

For the cheapest option look for ZCorp printing. ZCorp material starts life as a powder which is bound together layer by layer. They even can add color. However, it is somewhat fragile and low resolution with a 'sandy' surface.

The most common form of 3D printing is Fused Deposition Modeling (FDM). Some people like to call it 'glue-gun-on-a-stick' since you're basically extruding hot plastic (usually ABS) through a nozzle. The nozzle head moves back and forth creating your part line by line and layer by layer. Using professional equipment (e.g. Stratasys) the parts are usually medium resolution but durable. You'll find a wide range of prices from only slightly more than ZCorp to much greater. This is also the tech used by the homebrew and low cost printers you might have been hearing about so you might find someone that could print your part cheaply - but it will be lower resolution i.e. you'll see the layers.

Another option is Objet Polyjet printing (full disclosure: this is the equipment we use). Poly jet printing involves multi-head jetting of a layer of an acrylic photopolymer and following that with an immediate UV cure. Layers of 1/1000 of inch are created and details as small as 4 mils are possible. The finished part is durable and very high resolution - approaching that of SLS. Prices tend to be a bit higher than FDM but if you shop around (hint, hint) you'll find it comparably priced.

You could also check nylon sintering. It's ok resolution but relatively cheap and durable.

One final note: to 3d print you'll need to create a mesh of your part in STL format. Most 3D CAD programs will export in this format but be careful that your mesh is watertight and, if scaling, that your walls are all still thick enough for the material and equipment you're using. netfabb.com has a great free tool for checking/repairing stl files.

Good luck!

 

Hey Guys

Thank you for the reply.

I do not think I can do the whole platform in metal DMLS, however, I have a complex bracket. Its about 1 1/4" x 1" and not a lot of volume. To CNC machine this complex bracket you will need a 5 axis machine, I have already done it in SLA and it looks nice, now I just want to test it on the platform. This bracket will help with fabrication and welding so there will be little welds, this will help reduce costs in the log run to myself and the user.

Has anyone used the DMLS process? Can you recommend anyone?

Thank you again.

 

Hey Guys,

The complex bracket is fairly small little over an inch in x and about an inch in y. I do have this modeled up in Solidworks and I did send the files for quote in CNC and it is way too expensive apparently it has to be done on a 5 axis machine, which is why I thought of DMLS. Have you tried DMLS if so who? What did you think? As for the 3d printing, I did find a company that does what you are suggesting and also has DMLS, they are called GPI and I got my SLA from them, it looked great. I did get the DMLS cost from them also its about 1/10 of the CNC cost, which is great, but I want to know what you think of the actual DMLS part, they say it meets ASTM standards, its very strong like 40 HRC and can be polished etc. Is this all true? Thank you guys so much for your help!

 

Schmitty,
Sorry, I thought you were trying to get a model of the entire starting block.

IMO for the part you're describing DMLS would indeed be appropriate - for form and fit testing at least. For actual functional testing, under the load of a swimmer, it should also be fine, as these parts are typically melted to remove inherent porosity and increase structural integrity. DMLS parts are often used in extreme aerospace applications.

For actual production, if you're fine with the cost and speed of production (production time is going to be measured in hours as compared to minutes for CNC milling) by all means go with DMLS. But be sure to shop around for actual production run pricing for CNC milling; there are lots of machine shops out there hurting for business.

 

Regarding to the precise cnc machining and DMLS in China

Hi,Shmitty,

Firstly,2000.00USD is expensive if your project is small exactly.

Secondly,i still think cnc machining have more precise than direct metal laser sintering (DMLS).And could make the better effect than DMLS for the surface if choose cnc machining.

Would you like to let your project making in our factory?(send us the drawing and let me know your requirement about the surface finishing),we would quote for you as soon as possible with competitive.

www.jevny.com([email protected])

Precise cnc machining in China